\documentclass[twoside,letterpaper]{article}
\usepackage[T1]{fontenc}
\usepackage[marginparwidth=65pt, marginratio=1:1, tmargin=126pt, height=550pt, width=400pt]{geometry}

\begin{document}
\thispagestyle{empty}

Nullam auctor aliquet feugiat. Nam sed rutrum augue, id semper
ex. Integer malesuada euismod fermentum. Pellentesque vel dui lacinia,
maximus lacus mattis, tristique dui. Nam porta posuere diam, facilisis
cursus dui elementum venenatis varius velit.

\end{document}
